On Dec 12, 2014 8:33 AM, "Hector Marco" <hecma...@upv.es> wrote: > > Hello, > > I agree. I don't think a new randomization mode will be needed, just fix > the current randomize_va_space=2. Said other way: fixing the offset2lib > will not break any current program and so, no need to add additional > configuration options. May be we shall wait for some inputs > from the list (may be we are missing something). > > > Regarding to VDSO, definitively, is not randomized enough in 64bits. > Brute force attacks would be pretty fast even from the network. > I have identified the bug and seems quite easy to fix it. > > On 32bit systems, this is not a issue because it is mapped in the > mmap area. In order to fix the VDSO on 64bit, the following > considerations shall > be discussed: > > > Performance: > It seems (reading the kernel comments) that the random allocation > algorithm tries to place the VDSO in the same PTE than the stack.
The comment is wrong. It means PTE table. > But since the permissions of the stack and the VDSO are different > it seems that are getting right the opposite. Permissions have page granularity, so this isn't a problem. > > Effectively VDSO shall be correctly randomized because it contains > enough useful exploitable stuff. > > I think that the possible solution is follow the x86_32 approach > which consist on map the VDSO in the mmap area. > > It would be better fix VDSO in a different patch ? I can send a > patch which fixes the VDSO on 64 bit. > What are the considerations for 64-bit memory layout? I haven't touched it because I don't want to break userspace, but I don't know what to be careful about. --Andy > > > Regards, > Hector Marco. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
